DI.fm is free (http://www.di.fm/) and has loads of stations. I love the progressive channel mainly but ambient is nice to chill out to (especially to fall asleep to). It's ad-supported but you can pay $50 or so for a year and it's ad-free which is what I do.

Big fan of the Electro House station (which I found originally since notch was listening to it during a Ludum Dare livestream). Worth paying for the subscription to get rid of the ads, since they can throw you out of the flow easily.

DI.fm user since 2001. I switch between several stations (techno, trance, hardstyle, ...) and I've never been really bothered by the ads (except that it seems there have only the same two ads on every station for YEARS by now, but hey...).

I also mainly listen to electronic, as it helps me not lose my concentration, and is just a beat in background.

DI is amazing. I also really like Frisky Radio (http://www.friskyradio.com/) for what used to be known as progressive house when I was growing up. Now I think some of that 'big room' and 'drop' music is call prog house. That is more chill, spiritual, and have better flow from track to track so less distracting.

Great List! I see the same songs on my Glitch Mob station on Pandora. Jenkees is amazing. Also, I'm not sure why, but I just can't listen to anything with lyrics when I'm coding. Instrumentals all the way.

Mozart, Beethoven, and Rachmaninoff for normal coding. Helps you keep a nice rhythmic flow that relieves stress over long periods of time. I usually listen to this stuff when I have something that will take 8-30 hours to finish.

When a deadline is coming up, and I need to get a move on, I usually listen to heavy metal, rock and roll, maybe some classic rock.

Maybe I am odd, but I like listening to the last samurai soundtrack and similar. Heck, I even used the last of us soundtrack a few weeks back (spotify)... Also, long albums, like "the fragile" work too.

EDIT: Damn, I meant to reply to the OP. I too listen to Slayer when coding, though ;-)

I find it helps if I'm listening to music I'm already very familiar with; if I'm listening to Internet radio then I get sidetracked by checking out the artist bios and looking up their side projects on Wikipedia etc., and not getting much coding done!

Otherwise, I find minimalist techno and IDM work very well for me, here are some that I listen to a lot (Spotify links):

Lindsay Sterling and instrumental remixes of popular songs are my current favorite programming tunes. Other stuff I still go to: Thievery Corporation, Portishead, RJD2, The Submarines, anything classical, and many more I'm too lazy to type.